Ureteral stent with anti-migration features

ABSTRACT

Ureteral stents include a tubular body defining a lumen and have (i) a distal kidney section to be placed in or near a patient&#39;s kidney, (ii) a proximal bladder section to be placed within or near the patient&#39;s bladder, and (iii) a ureter section between the distal and proximal sections to be placed within the patient&#39;s ureter. A first anti-migration feature may be provided at the proximal bladder section and may include one or more projections extending outward from the tubular body. The first anti-migration feature may extend less than a total length of the proximal bladder section, and may be configured to not enter the patient&#39;s bladder. Furthermore, a second anti-migration feature may be provided at the distal kidney section, the proximal bladder section, or both.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.14/643,573, filed Mar. 10, 2015, which application is a non-provisionalapplication claiming the benefit of U.S. Provisional Application No.61/975,151 filed Apr. 4, 2014, the entire contents of which areincorporated herein by reference.

BACKGROUND

The invention relates to ureteral stents.

A ureter is a tubular passageway in the body that conveys urine from akidney to a bladder. Ureteral stents are used to facilitate urinarydrainage from the kidney to the bladder in patients having a ureteralobstruction or injury, or to protect the integrity of the ureter in avariety of surgical manipulations. Ureteral stents are typically about30 cm long, hollow catheter-like devices made from a polymer and placedwithin the ureter with the distal end residing in the kidney and theproximal end residing in the bladder. Ureteral stents function bychanneling the flow of urine from the kidney to the bladder. One or bothends of a ureteral stent may be coiled in a pigtail shape to prevent theupward and/or downward migration of the stent due to patient movement.For example, the ureter may stretch up to 5 cm in either directionduring a patient's normal bodily movements, such as movement duringbreathing. If the stent is not sufficiently anchored, this may result instent migration and displacement.

Another factor to be considered relates to tissue irritation caused bythe stent. A stent may cause tissue irritation due to the relativemovement between the stent and the ureter during natural stretching ofthe ureter, even when the stent is properly anchored. A typicalsemi-rigid, anchored stent is unable to adjust for the natural extensionand contraction of the ureter during bodily movements, resulting inpressure and irritation of the ureter and surrounding tissue.

Regions of tissue most vulnerable to stent-induced irritation includethe kidney, the renal pelvis, the sensitive bladder tissue in thetrigonal region, and tissue of the ureteral vesicle junction leadinginto the bladder. Irritation may be caused by the static or dynamiccontact of the semi-rigid stent with sensitive tissues of the body, suchas the kidney and the renal pelvis. Chronic trigonal tissue irritationmay result from contact of tissue by the bladder-anchoring features ofthe stent, for example, pigtails at the stent ends. Irritation problemsare of concern regardless of the duration of use of the stent.Irritation is of particular concern, however, when use of a stent isrequired over a long time period.

Another problem associated with ureteral stents is urine reflux and painduring urine voiding. On the initiation of voiding, the bladder wallmuscles contract causing the pressure inside the bladder to increase.Because a typical ureteral stent holds the ureteral orifice open,increased bladder pressure during voiding is transmitted to the kidneythrough the stent, causing urine reflux and flank pain.

SUMMARY

Many factors thus should be considered when designing a ureteral stent.Such factors include the function to be performed by different parts ofthe stent, such as anchoring, maintenance of an open-flow condition,etc., and comfort. In particular, it is desirable to make a ureteralstent that is easy to insert, comfortable at all times, exhibits goodcoil recovery (the tendency of the stent ends to return to theoriginally-designed coiled state after having been straightened, forexample, during insertion), remains anchored during normal bodilymovements, provides for suitable flow of urine, is easily removable andavoids fracture during insertion, use and removal. The invention relatesto various designs for a ureteral stent that facilitate some or all ofthe above goals.

Ureteral stents according to embodiments of the invention may include atubular body defining a lumen and having (i) a distal kidney section tobe placed in or near a patient's kidney, (ii) a proximal bladder sectionto be placed within or near the patient's bladder, and (iii) a uretersection between the distal and proximal sections to be placed within thepatient's ureter. A first anti-migration feature may be provided at theproximal bladder section and may include one or more projectionsextending outward from the tubular body. The first anti-migrationfeature may extend less than a total length of the proximal bladdersection, and may be configured to not enter the patient's bladder.Furthermore, a second anti-migration feature may be provided at thedistal kidney section, the proximal bladder section, or both.

The invention also relates to methods for providing drainage from akidney to a bladder within a patient in a ureteral stent. The methodsmay include deploying the ureteral stent from an outer sheath within aureter of a patient and sliding an outer layer of the ureteral stentfrom a first position to a second position to expose one or moreprojections on the ureteral stent such that the one or more projectionsmove from a delivery position in which the projections do not protrudebeyond an outer circumference of the tubular body, to a deploymentposition in which the projections protrude beyond the outercircumference of the tubular body and contact a ureteral wall of thepatient. Additionally, the methods may include locking the position ofthe outer layer with regard to the tubular body to lock the projectionsin the deployment position.

BRIEF DESCRIPTION OF THE DRAWINGS

Various exemplary embodiments of ureteral stents according to aspects ofthe invention will be described in detail with reference to thefollowing drawings in which:

FIGS. 1A-1C show ureteral stents according to embodiments of theinvention;

FIGS. 2A-2F show ureteral stents according to embodiments of theinvention;

FIG. 3 shows an anti-migration feature of a ureteral stent according toembodiments of the invention;

FIG. 4 shows an anti-migration feature of a ureteral stent according toembodiments of the invention;

FIG. 5 shows an anti-migration feature of a ureteral stent according toembodiments of the invention;

FIG. 6 shows an anti-migration feature of a ureteral stent according toembodiments of the invention;

FIG. 7 shows an anti-migration feature of a ureteral stent according toembodiments of the invention;

FIG. 8 shows an anti-migration feature of a ureteral stent according toembodiments of the invention;

FIGS. 9A and 9B show ureteral stents according to embodiments of theinvention;

FIG. 10 shows an expandable mesh-like anti-migration feature of aureteral stent according to embodiments of the invention;

FIG. 11 shows a ureteral stent with fold lines to form an anti-migrationfeature according to embodiments of the invention;

FIG. 12 shows a ureteral stent with fold lines to form an anti-migrationfeature according to embodiments of the invention;

FIG. 13 shows a distal end of a ureteral stent according to embodimentsof the invention; and

FIG. 14 shows a ureteral stent disposed within a patient's kidney,ureter and bladder.

DETAILED DESCRIPTION OF EMBODIMENTS

The disclosure relates to ureteral stents configured to reduce movementof the stent when deployed within a patient. As shown in FIG. 1A,ureteral stent 10 may include a tubular body 12 having a proximalbladder section 20, a distal kidney section 15, and a ureter section 25.The proximal bladder section 20 may be disposed at the proximal end 50of tubular body 12, and may be configured to be disposed in or near apatient's bladder. The distal kidney section 15 may be disposed at thedistal end 60 of tubular body 12, and may be configured to be disposedin or near the patient's kidney. As further shown in FIG. 1A, the uretersection 25 may be disposed between the proximal bladder section 20 andthe distal kidney section 15, and may be configured to be disposedwithin a patient's ureter.

Tubular body 12 may define a lumen 14 configured for the flow of fluidfrom the distal end 60 to the proximal end 50. The lumen 14 may be ofconstant diameter throughout the length of tubular body 12 (FIG. 1B).However, it is further contemplated that the lumen 14 may have varyingdiameters along the length of tubular body 12. For example, the lumen 14may have a relatively larger diameter at distal end 60 and a relativelysmaller diameter at proximal end 50. Alternatively, the lumen 14 mayhave a relatively larger diameter at proximal end 50 and a relativelysmaller diameter at distal end 60. Furthermore, the lumen 14 may includevarious cross-sectional configurations, for example, such as circular,square, etc. As is well known in the art, distal and proximal ends 60,50 can be open. Alternatively or additionally, the distal and proximalends 60, 50 can include perforations. Proximal end 50 may not extendthrough the ureteral orifice, and it may be made of a soft, flexiblematerial like silicone or other flexible, bacterial-resistant materialto reduce transverse forces on the bladder anatomy when the patientbends.

A first anti-migration feature 30 may be provided at the proximalbladder section 20, and a second anti-migration feature 40 may beprovided at the distal kidney section 15, the proximal bladder section20, or both. The first anti-migration feature 30 may be located at aportion of the longitudinal length of the tubular body such that thefirst anti-migration feature 30 is configured to not enter a patient'sbladder when the ureteral stent 10 is deployed with the patient.Therefore, for example, the first anti-migration feature 30 may beconfigured to not enter the patient's bladder when the proximal end 50of the proximal bladder section 20 is positioned within or near thepatient's bladder. In some embodiments, the first anti-migration feature30 may extend less than an entirety of a longitudinal length of theproximal bladder section 20, as shown in FIG. 1A. For example, the firstanti-migration feature 30 may extend for ¾, ⅔, ½, or ⅓ the length of theproximal bladder section 20. Preferably, the proximal-most end of thefirst anti-migration feature 30 is spaced from (distally spaced from)the proximal end 50 of the proximal bladder section 20. As shown in theembodiment of FIG. 1A, the first anti-migration feature extends a lengthL₁ and the proximal bladder section 20 extends a length L₂, wherein L₁is approximately ½ the length of L₂. The length of L₂ within theproximal bladder section is selected to provide sufficientanti-migration friction to counteract the natural peristaltic action ofthe ureter. In a preferred embodiment, the anti-migration feature 30locally increases the effective outer diameter of proximal bladdersection 20 by at least 20-50% over a length of approximately 3 cm. Amore substantial increase in diameter (i.e. 50-70%) can support ashorter anti-migration length (L₁). In some embodiments, the firstanti-migration feature 30 extends approximately the entire length of theproximal bladder section 20 such that L₁ is approximately equal to L₂.

The first and second anti-migration features 30, 40 may collectivelyreduce substantial migration of the ureteral stent 10. For example, thefirst anti-migration feature 30 may reduce retrograde movement of theureteral stent 10 (i.e., movement distally and away from the patient'sbladder), when the ureteral stent 10 is disposed within a patient.Additionally, the second anti-migration feature 40 may reduce antegrademovement of the ureteral stent 10 (i.e. movement proximally and towardthe patient's bladder). In some embodiments, the first and secondanti-migration features 30, 40 may prevent such movement of the ureteralstent 10. It is further contemplated that the ureteral stent 10 mayinclude only the first anti-migration feature 30 or the secondanti-migration feature 40 to reduce and/or prevent such movement of theureteral stent 10.

In some embodiments, the ureteral stent 10 may include the secondanti-migration feature 40 at both the proximal end 50 and distal end 60(FIG. 1C). In this embodiment, the second anti-migration feature 40 atthe proximal end 50 may further reduce and/or prevent retrogrademovement of the ureteral stent 10. For example, the secondanti-migration feature 40 at the proximal end 50 may be configured toextend into the patient's bladder. In some embodiments, the secondanti-migration feature 40 may be provided at only the proximal end 50 ofthe ureteral stent 10.

The second anti-migration feature 40, as described in further detailbelow, may alternatively refer to one or more features selected from alist including: a mesh structure configured to expand outward whenreleased from an outer sheath and a cross-sectional contouring providedto the first anti-migration feature 30.

The first anti-migration features 30 may be one or more projections 35extending radially outward away from an outermost surface of the tubularbody 12. As shown in FIG. 2A, the protrusions 35 may include a radiallyoutermost leading edge 37. An outermost diameter D₁ of the tubular body12 may be less than an outermost diameter D₂ of the radially outermostleading edge 37. The diameter D₂ may be, for example, 1.0-3.0 timeslarger than the diameter D₁. In some embodiments, the diameter D₂ may be1.2 to 1.5 times larger than diameter D₁, and for example, 1.3 timeslarger.

As shown in FIG. 2A, the projections 35 may extend a distance T₁ from atop surface of the tubular body 12, and the projections 35 may extend adistance T₂ from a bottom surface of the tubular body 12. Distance T₁may be equal to, larger than, or smaller than T₂ such that the radiallyoutermost leading edge 37 may be constant or of varying dimensions alongtubular body 12. As shown in FIG. 2A, T₁ and T₂ are approximately equal.It is further contemplated that the radially outermost leading edge 37may comprise varying shapes. For example, when viewed in cross-section,leading edge 37 may form a rounded configuration (FIG. 2B), a squareconfiguration (FIG. 2C), a triangular configuration (FIG. 2D), a U-shapeconfiguration (FIG. 2E), and/or a wave configuration (FIG. 2F).Additionally or alternatively, the leading edge 37 may include achamfered surface. One or more projections 35 may include a leading edge37 with configurations different from one or more other projections 35on tubular body 12. For example, half of the projections 35 closer toproximal end 50 may comprise a leading edge 37 with a squareconfiguration (FIG. 2C) and half of the projections 35 closer to thedistal end 60 may comprise a leading edge 37 with a roundedconfiguration (FIG. 2B). In some embodiments, the second anti-migrationfeature 40 may be provided as a shape contouring to the firstanti-migration feature 30. For example, the second anti-migrationfeature 40 may include shapes as shown in FIGS. 2B-2F that contour tothe first anti-migration feature 30.

The projections 35 may form a spiral 70, as shown in FIG. 2A, such thatthe spiral 70 forms one continuous helical structure along a predefinedlength of tubular body 12. In some embodiments, spiral 70 may includetwo or more helical segments, wherein each helical segment forms acontinuous structure along a predefined length of tubular body 12. Thespiral 70 may be oriented at an angle Θ with regard to the outermostsurface of the tubular body, and may include a pitch P. The angle Θand/or pitch P may be constant or may vary along the length of tubularbody 12. For example, the angle Θ may be relatively larger and the pitchP may be relatively smaller closer to the proximal end 50.

In some embodiments, as shown in FIG. 3, the projections 35 may be oneor more rings 80, wherein each ring 80 is separated from an adjacentring 80 by distance S. The distance S between each ring may be constantor may vary along the length of tubular body 12. For example, S may besmaller closer to the proximal end 50.

In other embodiments, the projections 35 may be one or more pads(protrusions) 90. For example, as shown in FIG. 4, each pad 90 mayinclude a raised structure that is separated from each adjacent pad 90.A plane traversing each pad 90 in a longitudinal direction may traverseat least one other pad, and a plane traversing each pad in a crosswisedirection, perpendicular to the longitudinal direction, may traverse atleast one other pad. The pads 90 may each comprise approximately equalsurface areas, or the pads 90 may comprise varying surface areas. Forexample, the pads 90 closer to the proximal end 50 may compriserelatively larger surface areas. Additionally, the pads 90 may be rigid,and they may be made of the same or of a different material than tubularbody 12. In some embodiments, the pads 90 may be made from a differentmaterial than the tubular body and include a tacky character such aspolyurethane, silicone, or PEBAX (polyether block amide). The pads 90may be made from the same base material as the tubular body 12, but maybe altered to be more tacky. It is contemplated that the pads 90 mayfurther comprise shape contouring as a second anti-migration feature 40,for example as shown in FIGS. 2B-2F. It is further contemplated that thetubular body 12 may include a coating, for example a hydrophiliccoating, but that the pads 90 preferably are not coated. This improvesthe anti-migration function of the pads 90.

According to some embodiments, the first anti-migration feature 30 maybe one or more protrusions 100 configured to move from a retracteddelivery position (FIG. 5), in which the protrusions 100 do not protruderadially beyond an outer circumference of the tubular body 12, to aprotracted deployment position (FIG. 6), in which the protrusions 100protrude radially outward beyond the outer circumference of the tubularbody 12. For example, a slideable outer tube 110 (e.g., outer layer) maybe disposed co-axial and outward of the tubular body 12. The outer tube110 may include one or more apertures 120 through which the protrusions100 protrude when in the deployment position.

As shown in FIG. 5, when in the delivery position, the protrusions 100may be disposed between the outer tube 110 and the tubular body 12. Theprotrusions 100 may be substantially co-axial with the outer tube 110and tubular body 12 when the protrusions 100 are in the deliveryconfiguration. The protrusions 100 may be of a spring-like material suchthat a radially inward force (e.g., toward the tubular body 12) exertedby the outer tube 110 prevents the protrusions from projecting outwardwhen in this delivery position. Movement of the outer tube 110 relativeto the protrusions 100 may align the protrusions 100 with apertures 120,disposed on the outer tube 110, such that the protrusions 100 mayproject through the apertures 120 and assume their delivery position.Therefore, the radially inward force from the outer tube 110 may beremoved and the protrusions 100 may assume their delivery position. Itis further contemplated that the protrusions 100 may move relative tothe outer tube 110 to align the protrusions with the apertures 120.

As shown in FIG. 6, when in the deployment position, a portion of theprotrusions 100 may remain disposed between the tubular body 12 and theouter tube 110. This portion of the protrusions 100 may remain securedto the outer tube 12 through any suitable attachment means, such as, forexample, a clip, adhesive, screw, thermal coupling, etc.

The protrusions 100 may be deployed and assume their deliveryconfiguration only after the ureteral stent 10 has been delivered to thedeployment site within the patient. Therefore, for example, theprotrusions 100 may project into ureteral wall tissue of the patientwhen the protrusions 100 project through apertures 120. This mayfacilitate securing the ureteral stent 10 within the patient andreducing/preventing retrograde movement of the ureteral stent 10. Afterthe ureteral stent 10 is no longer needed and with the protrusions 100still deployed, the ureteral stent 10 may be removed from the patientwithout retracting the protrusions 100 within the outer tube 110 due tothe angle at which the deployed protrusions 100 extend. Therefore, theprotrusions 100 may remain deployed, and thus in their deploymentposition, when the ureteral stent 10 is removed from the patient. Inother embodiments, the outer tube 110 may be moved relative to theprotrusions 100 to fully retract the protrusions 100 within the outertube 110 (FIG. 5) before the ureteral stent 10 is removed from thepatient.

FIG. 7 shows the ureteral stent of FIGS. 5 and 6 used with aninsertion/extraction tool 130. When the ureteral stent 10 is to beinserted into a patient, the insertion/extraction tool 130 is insertedinto the proximal end 50 of the stent such that a button (a lockingmechanism) 135 that is spring-biased radially outward fits into anopening (hole) 145 in the outer tube 110. The insertion/extraction tool130 can be used to push and/or pull the ureteral stent 10 into position.For example, when it is desired to deploy the protrusions 100, theinsertion/extraction tool 130 may be pulled proximally, which causes theouter tube 110 to move proximally relative to the tubular member 12 andto the protrusions 100. This causes the protrusions 100 to becomealigned with the apertures 120 of the outer tube 110, and thereby movefrom the delivery position to the deployment position shown in FIG. 7.As the outer tube 110 is moved proximally, a slide-lock 140, which ispart of the outer tube 110, may move radially inward to the positionshown in FIG. 7. Because the slide-lock 140 has moved radially inward,the outer tube 110 cannot be moved distally relative to the tubular body12. The protrusions 100 thus remain in the deployed position shown inFIG. 7. The button 135 can be moved radially inward so that it no longerextends into the hole 145, and then the insertion/extraction tool 130can be removed from the ureteral stent 10.

The second anti-migration feature 40 may include one or more featuressuitable to reduce and/or prevent antegrade movement of the ureteralstent 10. For example, as shown in FIG. 8, the second anti-migrationfeature 40 may include a coiled structure 160. As shown in FIGS. 8 and14, the coiled structure 160 may be configured to longitudinally extendfrom a tightly coiled state (FIG. 8) to a loosely coiled state (FIG.14). This extension may be due to movement of the patient, for examplewhen the patient is breathing.

One or more holes 170 may be disposed on the coiled structure 160, andthe holes 170 may be of sufficient size for fluid flowing within lumen14 to exit the tubular body 12. It is further contemplated that theholes 170 are disposed along at least a portion of the proximal bladdersection 20 and/or the ureter section 25. For example, the holes 170 maybe disposed along the entire length of tubular body 12.

The proximal end 50 of the tubular body 12 may include valve 180. Asshown in FIG. 9A the valve 180 may be disposed centrally with regard toa central axis C of the tubular body 12. In other embodiments, as shownin FIG. 9B, the valve may 180 may be disposed lateral to the centralaxis C of the tubular body 12. The valve 180 may be a one-way valve suchthat fluid within lumen 14 may only flow out of the lumen 14 via thevalve 180, and not into lumen 14 via the valve 180.

In some embodiments, the second anti-migration feature 40 may include amesh structure 190 configured to expand outward when released from anouter sheath 220. As shown in FIG. 10, the mesh structure 190 mayinclude a middle mesh layer 200 surrounded by an outer layer 205 and aninner layer 210. The middle mesh layer 200 may be biased to assume anexpanded configuration when released from the sheath 220, and the middlemesh layer 200 may be comprised of a network of interlocking struts. Themiddle mesh layer 200 may include for example, a superelastic alloy suchas Nitinol. The outer layer 205 may provide a coating on the mesh layer200 to reduce friction between the outer sheath 220 and the mesh layer200. Additionally, the inner layer 210 may provide a coating on themiddle mesh layer 200 to facilitate the flow of fluid within the lumen14. In some embodiments, the outer layer 205 and inner layer 210 mayinclude, for example, a polymeric material. For example, the outer layer205 may comprise polyurethane, PEBAX (polyether block amide), a lowfriction polymer including TEFLON (PTFE), FKM (Viton, Fluorel, Aflas),or mixtures thereof. The inner layer 210 may comprise a hydrophilic orpolar polymer including, for example, polyurethane or PEBAX (polyetherblock amide) or mixtures thereof.

Movement of the outer sheath 220 relative to the mesh structure 190 mayallow the ureteral stent 10 to move from a delivery position, in whichthe mesh structure 190 is disposed within the sheath 220, to adeployment position, in which the mesh structure 190 is removed from thesheath 220. As shown in FIG. 10, the mesh structure 190 may expand to adiameter larger than an outer diameter of the remainder of the tubularbody 20 when in the deployed position. For example, a mesh coated with aflexible material like silicone may be permitted to expand as shown inFIG. 10. This mesh may be restricted to the distal kidney section 15 ofthe stent and may have a different cross section than the remainder ofthe tubular body 12. In another embodiment, mesh structure 190 may befabricated of the same material as the remainder of the tubular body 12,but with a smaller wall thickness so as to be more flexible to morereadily form the second anti-migration feature 40.

The tubular body 12 may include one or more fold lines 230 such that thetubular body 12 is configured to collapse upon the fold lines 230 whenin a delivery configuration, for example as shown in FIG. 11. The foldlines 230 may include preformed grooves, indentations, or slits toenable the tubular body 12 to collapse and fold upon the fold lines 230.The fold lines 230 in tubular body 12 may be formed into a super-elasticmetal mesh, such as one made of nitinol wire, or formed into a polymericmaterial with self-expanding capabilities. The fold lines 230 cut intotubular body 12 may include multiple layers of mesh, with an outer meshlayer being capable of greater expansion diameters than an inner meshlayer. The inner mesh layer may provide additional anchoring support tothe outer mesh layer in the deployment position and may contribute to asuperior anchoring capability. The elastic restoring force of the innermesh layer may provide additional force to secure the ureteral stent 10in position during deployment. The mesh may be woven or non-woven,collapsible, and self-expanding. The self-expansion may arise from anelastic restoring force to engage the mesh with the surrounding tissue.In some embodiments, the outer mesh layer may expand into a contouredouter shape, being formed into different cross sectional profiles, suchas rounded, triangular, square shaped, U-shaped, or wave shaped. It iscontemplated that individual wires within the mesh may be shaped with arounded, triangular, square shaped, U-shaped or wave shapedconfiguration as illustrated in FIGS. 2B-2F to provide additionalanchoring support. As shown in FIGS. 11 and 12, the tubular body 12 mayexpand radially outward from the fold lines 230 upon removal of theouter sheath 220.

The tubular body 12 may comprise a material suitable to withstandmultiple compression and relaxation cycles of a patient's bladderwithout breaking. Suitable materials include, for example, polymericmaterials, such as polyurethane, silicone, PEBAX (polyether blockamide), or any biocompatible thermoplastic elastomer. In someembodiments, the distal kidney section 15 of the tubular body 12 may becomprised of a different material than the ureter section 25 and/or theproximal bladder section 20. For example, the distal kidney section 15may comprise a relatively more flexible material than the ureter section25 and/or the proximal bladder section 20. A more flexible distal kidneysection 15 may allow the distal kidney section 15 to bend and collapseunder pressure from a patient's kidney (for example, during urinevoiding), and therefore reduce discomfort that is typically associatedwith a traditional ureteral stent. In some embodiments, the distalkidney section 15 may be thinner and may comprise a relatively stiffermaterial than the proximal bladder section 20 in order to reduce suchdiscomfort. Additionally or alternatively, the distal kidney section 15may comprise one or more depressions 240, as shown in FIG. 13. Thedepressions 240 may provide adequate flexibility to the distal kidneysection 15 of tubular body 12 to reduce such discomfort. The depressions240 may include slits, holes, or indentations in the distal kidneysection 15. Alternatively or additionally, the depressions 140 mayinclude a material sufficient to provide such flexibility to the distalkidney section 15. This material may be the same or different from thematerial of the remainder of the tubular body 12.

The inner and/or outer surfaces of the tubular body 12 may be coated.For example, the inner surface may be coated with a lubricious coatingto facilitate the flow of fluid within lumen 14. In some embodiments,the inner surface coating may substantially prevent the growth ofbiofilm. The outer surface may be coated with, for example, ahydrophilic coating to promote the attachment of the ureteral stent 10to the ureter wall of a patient.

As shown in FIG. 14, the ureteral stent 10 may be delivered to theureter 300 of a patient with, for example, outer sheath 220. In thisexample, the ureteral stent 10 may be positioned within a patient suchthat the distal end 60 is disposed within the patient's kidney 310 andthe proximal bladder section 20 does not enter the patient's bladder320. The distal kidney section 15 is thus secured within the kidney 310to prevent and/or reduce antegrade movement of the ureteral stent 10.Furthermore, the proximal bladder section 20 is positioned such that itdoes not enter the bladder 320 but still provides a secure attachment tothe wall of the ureter 300 to prevent and/or reduce retrograde movementof the ureteral stent 10. Thus, ureteral stent 10 may not contact thesensitive bladder tissue in the trigonal region of a patient and therebyreduce pain and discomfort for the patient. In some embodiments, theureteral stent 10 may be positioned such that the proximal end 50 doesnot enter the patient's bladder 320. The first and second anti-migrationfeatures 30, 40 allow the ureteral stent to remain fixed in place withinthe patient while the ureteral stent 10 reduces such pain anddiscomfort. Thus, ureteral stent 10 advantageously provides increasedpatient comfort.

What is claimed is:
 1. A ureteral stent comprising: a tubular bodydefining a lumen and having (i) a distal kidney section to be placed inor near a patient's kidney, (ii) a proximal bladder section to be placedpartly within or near the patient's bladder, and (iii) a ureter sectionbetween the distal and proximal sections to be placed within thepatient's ureter; a first anti-migration feature provided entirely atthe proximal bladder section and including one or more projectionsextending outward from the tubular body, the first anti-migrationfeature being distally spaced from a proximal end of the tubular body;and a second anti-migration feature provided at the distal kidneysection, the second anti-migration feature including a coiled structure,wherein the one or more projections include a set of pads that areseparated from each other, and a first subset of the pads closer to aproximal end of the tubular body have a relatively larger surface areathan a second subset of the pads closer to a distal end of the tubularbody.
 2. The ureteral stent of claim 1, wherein the secondanti-migration feature is provided at both the distal kidney section andthe proximal bladder section.
 3. The ureteral stent of claim 1, whereinthe first anti-migration feature includes a plurality of protrusionssuch that one or more protrusions include a leading edge with adifferent configuration from one or more other protrusions.
 4. Theureteral stent of claim 1, further comprising a slideable outer tubethat is co-axial with the tubular body.
 5. The ureteral stent of claim1, wherein the distal kidney section is more flexible than at least oneof the ureter section and the proximal bladder section.
 6. The ureteralstent of claim 1, wherein the second anti-migration feature includesdepressions in an outer surface of the tubular body.
 7. A ureteral stentcomprising: a tubular body defining a lumen and having (i) a distalkidney section to be placed in or near a patient's kidney, (ii) aproximal bladder section to be placed partly within or near thepatient's bladder, and (iii) a ureter section between the distal andproximal sections to be placed within the patient's ureter; a firstanti-migration feature provided entirely at the proximal bladder sectionand including one or more projections extending outward from the tubularbody, the first anti-migration feature being configured to not enter thepatient's bladder; and a second anti-migration feature provided at thedistal kidney section, the second anti-migration feature including atleast of a coiled structure, a mesh structure, and a cross-sectionalcontouring provided to the first anti-migration feature, wherein the oneor more projections include a set of pads that are separated from eachother, and a first subset of the pads closer to a proximal end of thetubular body have a relatively larger surface area than a second subsetof the pads closer to a distal end of the tubular body.
 8. The ureteralstent of claim 7, wherein: the second anti-migration feature is the meshstructure, and the mesh structure includes a middle mesh layer that issurrounded by an outer layer and an inner layer, the outer layer and theinner layer providing coatings on the middle mesh layer.
 9. The ureteralstent of claim 8, further comprising a slideable outer sheath.
 10. Theureteral stent of claim 9, wherein the mesh structure is configured toexpand outward when released from the outer sheath.
 11. The ureteralstent of claim 7, wherein the tubular body includes one or more foldlines such that the tubular body is configured to collapse upon the foldlines when in a delivery configuration.
 12. The ureteral stent of claim11, wherein the fold lines include preformed indentations.
 13. A systemcomprising: the ureteral stent of claim 1; a slideable outer tube thatis co-axial with the tubular body; and an insertion/extraction tool thatis configured to be inserted into a proximal end of the tubular body topush and/or pull the ureteral stent.
 14. The system of claim 13, whereinthe insertion/extraction tool includes a locking mechanism that isspring-biased to protrude into an opening on the outer tube.
 15. Thesystem of claim 13, wherein the outer tube includes a slide-lock that isconfigured to prevent the outer tube from moving distally relative tothe tubular body.
 16. The system of claim 13, wherein the outer tubeincludes one or more apertures through which the one or more projectionsprotrude when in a deployment position.
 17. A ureteral stent comprising:a tubular body defining a lumen and having (i) a distal kidney sectionto be placed in or near a patient's kidney, (ii) a proximal bladdersection to be placed partly within or near the patient's bladder, and(iii) a ureter section between the distal and proximal sections to beplaced within the patient's ureter; a first anti-migration featureprovided at the proximal bladder section and including one or moreprojections extending a distance radially outward from an outermost topsurface of the tubular body, the first anti-migration feature extendingdistal of a proximal end of the tubular body; and a secondanti-migration feature provided at the distal kidney section, the secondanti-migration feature including a coiled structure, wherein the one ormore projections include a set of pads that are separated from eachother, and a first subset of the pads closer to a proximal end of thetubular body have a relatively larger surface area than a second subsetof the pads closer to a distal end of the tubular body.